Power generating wind turbine

ABSTRACT

A power generating wind turbine includes parts and components installed in or on a nacelle which are made smaller and lighter, thus facilitating maintenance. A main shaft  11 , a gear-box for speeding up rotation of the main shaft  11  and a generator  13  driven by an output of the gear-box  11  are provided on a nacelle bed plate  6 . The main shaft  11  is connected to an input shaft  12   a  end of the gear-box  12  via a double-row tapered roller bearing  16 . The main shaft  11  is supported to a wall portion W 1  of the nacelle bed plate  6  with the double-row tapered roller bearing  16  being interposed therebetween. The main shaft  11  is formed in an annular shape having its outer diameter D 1  larger than its axial directional length L 1.

TECHNICAL FIELD

The present invention relates to a power generating wind turbine.

BACKGROUND ART

A power generating wind turbine comprises a nacelle installed on atower, a wind turbine rotating blade, a gear-box inputted with a windforce received by the wind turbine rotating blade via a main shaft and agenerator driven by an output of the gear-box. Such power generatingwind turbine is known, for example, by Patent Documents 1 to 3 asmentioned below.

In the Patent Document 1, for example, a power generating wind turbineis disclosed having a structure in which a rotor provided with a windturbine rotating blade is directly installed on a planetary carrier of agear-box to be supported to the gear-box.

Also, in the Patent Document 2, a power generating wind turbine isdisclosed having a structure in which a rotor hub is directly installedon a planetary holder to be supported to a gear-box.

Further, in the Patent Document 3, a power generating wind turbine isdisclosed having a structure in which a rotor is assembled into agear-box to be supported to the gear-box. An annular gear carrier and anannular gear of the gear-box are directly fitted to this rotor so thatthe rotor itself constitutes a portion of the gear-box.

-   -   Patent Document 1: European laid-open patent application No.        0811764 (3rd Column and FIG. 1)    -   Patent Document 2: World laid-open patent application No.        02/079644 (4th Column and FIG. 2)    -   Patent Document 3: US laid-open patent application No.        2002/0049108 (Abstract and Figures)

In the prior art power generating wind turbines, however, there areshortcomings as follows: That is, the construction is made such that thewind turbine rotating blade and the rotor are supported to the gear-boxand hence the gear-box and the gear-box supporting members are requiredto have a sufficient strength to withstand a load added to the rotor,such as a radial load, thrust load and bending load.

The size of the gear-box is decided depending not only on its speed-upratio but also on its required strength. That is, even if a speed-upratio is the same, a gear-box for which a higher strength is required isinevitably made larger to that extent. For this reason, the powergenerating wind turbines disclosed in the Patent Documents 1 to 3 needto be provided with a large size gear-box.

Such a large size gear-box has a heavy weight and hence the load addingto the gear-box, nacelle and tower supporting the nacelle also becomeslarge. Thus, these parts and components are required to have a higherstrength, and this results in these parts and components having a largesize and heavy weight.

In the prior art power generating wind turbine, therefore, there areproblems not only in the manufacturing cost but also in thetransportation and installation work of each of the constructional partsand components, such as the gear-box, nacelle, tower or the like.

Moreover, by using such a large size gear-box, a space in the nacellebecomes narrower and the freedom of structure of the nacelle and thefreedom of arrangement of the parts and components installed in thenacelle become smaller so that the design becomes difficult.

Also, in such construction of the rotor being supported to the gear-box,if the gear-box is to be overhauled for maintenance, the rotor must beonce taken out of the gear-box and placed on the ground. Thus, themaintenance work becomes very troublesome.

SUMMARY OF THE INVENTION

In view of the problems in the prior art, it is an object of the presentinvention to provide a power generating wind turbine in which parts andcomponents provided in the nacelle can be made compact in size and lightin weight and the maintenance can be facilitated.

In order to achieve the above-mentioned object, a power generating windturbine of the present invention is constructed by the means as follows:

That is, in a first aspect of the invention, a power generating windturbine comprising a nacelle installed on a tower, the nacellecomprising therein or thereon a main shaft to which a wind turbinerotating blade is fitted, a gear-box by which a rotation of the mainshaft is speeded up to be put out and a generator driven by an output ofthe gear-box, is characterized in that the main shaft is connected to anend of an input shaft of the gear-box and is supported to the nacellevia a single double-row tapered roller bearing.

In the power generating wind turbine of the present invention, the mainshaft is supported by the single double-row tapered roller bearing thatis provided in the nacelle. The double-row tapered roller bearing isprovided in a single unit and thereby the radial load, thrust load andbending load adding to the supporting shafts can be received. That is,all the radial load, thrust load and bending load adding to the mainshaft are received by this single double-row tapered roller bearing.

In this way, in the power generating wind turbine of the presentinvention, the main shaft is supported by the single double-row taperedroller bearing and thereby the supporting structure of the main shaftcan be made compact.

Also, the radial load, thrust load and bending load adding to the mainshaft are received by the double-row tapered roller bearing and therebythe strength required of the gear-box can be made smaller.

The size of the gear-box is decided depending not only on its speed-upratio but also on its strength required. In the power generating windturbine of the present invention, the strength so required of thegear-box can be made smaller and hence, as the gear-box, such one as issmaller in size and lighter in weight can be used as compared with thatused in the prior art power generating wind turbine.

Also, the main shaft is connected to the input shaft of the gear-box soas to be separable from each other. Hence, in case of maintenance of thegear-box, the gear-box and the main shaft are separated from each otherand maintenance of the gear-box only can be carried out. Likewise, incase of maintenance of the main shaft, the main shaft and the gear-boxare separated from each other and maintenance of the main shaft only canbe carried out.

Also, in a second aspect of the invention, a power generating windturbine comprising a nacelle installed on a tower, the nacellecomprising therein or thereon a main shaft to which a wind turbinerotating blade is fitted, a gear-box by which a rotation of the mainshaft is speeded up to be put out and a generator driven by an output ofthe gear-box, is characterized in that the main shaft is connected to anend of an input shaft of the gear-box and is supported to the nacellevia a single three-row roller bearing comprising a row of rollersreceiving a radial load and a pair of rows of rollers receiving a thrustload.

In the power generating wind turbine of the present invention, the mainshaft is supported by the single three-row roller bearing that comprisesa row of rollers receiving the radial load and a pair of rows of rollersreceiving the thrust load. Thereby, the supporting structure of the mainshaft can be made compact.

Also, the radial load, thrust load and bending load adding to the mainshaft are received by each of the rows of the roller bearing and therebythe strength required of the gear-box and the gear-box supportingmembers can be made smaller.

The size of the gear-box is decided depending not only on its speed-upratio but also on its strength required. In the power generating windturbine of the present invention, the strength so required of thegear-box can be made smaller and hence, as the gear-box, such one as issmaller in size and lighter in weight can be used as compared with thatused in the prior art power generating wind turbine.

Also, the main shaft is connected to the input shaft of the gear-box soas to be separable from each other. Hence, in case of maintenance of thegear-box, the gear-box and the main shaft are separated from each otherand maintenance of the gear-box only can be carried out. Likewise, incase of maintenance of the main shaft, the main shaft and the gear-boxare separated from each other and maintenance of the main shaft only canbe carried out.

In a third aspect of the invention, a power generating wind turbine asmentioned in the first or second aspects is characterized in that themain shaft is formed in an annular shape or a disk shape having itsouter diameter made larger than its axial directional length.

In the power generating wind turbine constructed as mentioned above, theouter diameter of the main shaft is set larger as compared with theaxial directional length of the main shaft, that is, the ratio of theouter diameter to the axial directional length is set larger. That is,the axial directional length is contracted as compared with the priorart main shaft. Nevertheless, in the main shaft, a space sufficient forinstalling the double-row tapered roller bearing or the three-row rollerbearing is secured.

Thereby, the axial directional length of the main shaft is suppressedand the weight of the main shaft can be reduced.

Also, the bending moment adding to the main shaft when the wind turbinerotating blade receives the wind force becomes less and the strengthrequired of the main shaft and the main shaft supporting members can bemade smaller. By so making smaller the strength required of the mainshaft and the main shaft supporting members, the main shaft and the mainshaft supporting members can also be made smaller.

In a fourth aspect of the invention, a power generating wind turbine asmentioned in the first or second aspects is characterized in that themain shaft and the input shaft of the gear-box are connected to eachother via a coupling. Also, in a fifth aspect of the invention, a powergenerating wind turbine as mentioned in the third aspect ischaracterized in that the main shaft and the input shaft of the gear-boxare connected each other via a coupling.

In the power generating wind turbine constructed as mentioned above, themain shaft and the input shaft of the gear-box are connected to eachother via the coupling and hence an adjusting work requiring skills,such as an alignment adjustment of the main shaft and the input shaft orthe like, becomes unnecessary and the assembling and maintenance thereofare facilitated.

By the coupling also, transmission of the radial load, thrust load andbending load from the main shaft to the gear-box is prevented and thestrength required of the gear-box can be made further smaller.

Hence, as the coupling of the present invention, a gear coupling, diskcoupling, connecting structure by a bush, connecting structure by a pinor otherwise a coupling of an arbitrary type can be used.

As a summary, in the power generating wind turbine according to thepresent invention, the parts and components, such as the supportingstructure of the main shaft, the gear-box or the like, that areinstalled in or on the nacelle can be made smaller in size and lighterin weight and hence the nacelle can be made smaller and lighter. Also,by so making the nacelle and the parts and components installed in or onthe nacelle smaller and lighter, the transportation and installationwork of the nacelle and other parts and components can be facilitated.Also, the load adding to the tower that supports these parts andcomponents becomes less and the structure of the tower can besimplified.

Further, the main shaft and the gear-box are structurally made separablefrom each other and thereby maintenance of these components can becarried out independent of each other and the maintainability isenhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a power generating wind turbine of a firstembodiment according to the present invention.

FIG. 2 is a cross sectional side view showing a construction of anacelle of the power generating wind turbine of the first embodiment ofFIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 2.

FIG. 4 is a cross sectional side view of a power generating wind turbineof a second embodiment according to the present invention.

FIG. 5 is a cross sectional side view showing a modified construction ofthe power generating wind turbine of the second embodiment of FIG. 4.

FIG. 6 is a cross sectional side view showing another modifiedconstruction of the power generating wind turbine of the secondembodiment of FIG. 4.

FIG. 7 is a cross sectional side view showing still another modifiedconstruction of the power generating wind turbine of the secondembodiment of FIG. 4.

FIG. 8 is a cross sectional side view showing one modified example ofthe power generating wind turbine according to the present invention.

FIG. 9 is a cross sectional side view showing one modified example ofthe power generating wind turbine according to the present invention.

FIG. 10 is a cross sectional side view showing one modified example ofthe power generating wind turbine according to the present invention.

FIG. 11 is a cross sectional side view showing one modified example ofthe power generating wind turbine according to the present invention.

FIG. 12 is a cross sectional side view of a power generating windturbine of a third embodiment according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Herebelow, the present invention will be described more in detail basedon embodiments according to the present invention with reference to theappended drawings.

First Embodiment

A first embodiment according to the present invention will be describedwith reference to FIGS. 1 to 3.

A power generating wind turbine 1 of the present embodiment, as shown inFIG. 1, comprises a tower 2 provided to rise on a base B, a nacelle 3provided on an upper end of the tower 2 and a rotor head 4 provided ontothe nacelle 3 so as to be rotatable around a substantially horizontalaxis. A plurality of wind turbine rotating blades 5, arranged radiallyaround a rotational axis of the rotor head 4, are fitted to the rotorhead 4, so that a wind force working on the wind turbine rotating blades5 from a rotating axis direction of the rotor head 4 is converted intopower to rotate the rotor head 4 around the rotational axis thereof.

The tower 2 is constructed, for example, by a plurality of towercomponents being vertically piled one on another. The nacelle 3 isinstalled on the uppermost one of the tower components constituting thetower 2. The nacelle 3 comprises a nacelle bed plate 6 (FIG. 2) fittedto the upper end of the tower 2 and a cover 7 (FIG. 1) covering thenacelle bed plate 6 from above.

The nacelle bed plate 6 is provided to be rotatable on a horizontalplane relative to the tower 2 so that, when the nacelle bed plate 6 isdriven by a drive unit (not shown), the nacelle 3 can change itsdirection on the horizontal plane.

The nacelle bed plate 6, as shown in FIG. 2, comprises a floor portion 6a to be fitted substantially horizontally to the upper end of the tower2 and a shell body 6 b covering the floor portion 6 a from above. Theshell body 6 b comprises a wall portion W1 rising from a connectingportion between the shell body 6 b and the floor portion 6 a and a domeportion W2 connecting together a peripheral edge portion of the wallportion W1 and the floor portion 6 a.

Also, a first opening portion H1 is formed in the wall portion W1 and asecond opening portion H2 is provided in the dome portion W2 at aposition opposed to the first opening portion H1. Through these firstand second opening portions H1, H2, the parts and components to beprovided inside or outside of the nacelle bed plate 6 are assembled tobe connected to each other.

As shown in FIG. 2, the nacelle bed plate 6 is provided with a mainshaft 11, a gear-box 12 speeding up a rotation of the main shaft 11 tobe put out and a generator 13 driven by an output of the gear-box 12.

The gear-box 12 is provided in the nacelle bed plate 6 and the generator13 is arranged outside of the nacelle bed plate 6 at a position opposedto the second opening portion H2 of the dome portion W2. The gear-box 12and the generator 13 are fixed to the nacelle bed plate 6 via a stay orthe like (not shown).

An input shaft 12 a is connected to the gear-box 12 through the firstopening portion H1 so that a rotation of the input shaft 12 a around theaxis relative to the main shaft 11 is regulated. Thereby, the rotationinputted into the input shaft 12 a from the main shaft 11 is speeded upso as to meet a rotational speed appropriate for the generator 13 and isput out to an output shaft 12 b.

The gear-box 12 of the present embodiment carries out a speed-up of onestage or plural stages and, for example, between the input shaft 12 aand the output shaft 12 b, a planetary stage using planetary gears and aparallel stage using spur gears are provided in series in one stage orplural stages, respectively. By these respective planetary stage andparallel stage, the rotation inputted into the input shaft 12 a isspeeded up to be finally put out to the output shaft 12 b with anappropriate rotational speed.

Also, a generator shaft (not shown) of the generator 13 is connected tothe output shaft 12 b of the gear-box 12 through the second openingportion H2 so that a rotation of the generator shaft around the axisrelative to the output shaft 12 b of the gear-box 12 is regulated. Thus,by the rotation of the output shaft 12 b, the generator 13 is driven sothat electricity is generated.

As the generator 13, an arbitrary type of generator, such as aninduction type, wound type, secondary resistance control wound inductiontype (rotor current control or RCC type), secondary excitation controlwound induction type (static Scherbius or D.F. type), synchronous type,permanent magnet type, induction multiple type, etc. can be used.

The main shaft 11 is arranged outside of the nacelle bed plate 6 at aposition opposed to the first opening portion H1 of the wall portion W1.The main shaft 11 is provided having its one end in the axial directiondirected to the first opening portion H1. A double-row tapered rollerbearing 16 is interposed between the main shaft 11 and the wall portionW1 and the main shaft 11 is connected to a distal end of the input shaft12 a of the gear-box 12 via the double-row tapered roller bearing 16.

Also, the main shaft 11 has the other end in the axial directionconnected to the rotor head 4 so that a rotation of the rotor head 4around the rotational axis relative to the main shaft 11 is regulated.Thereby, the rotor head 4 and the main shaft 11 integrally rotate aroundthe axis.

The double-row tapered roller bearing 16 is provided coaxially with themain shaft 11 between the one end in the axial direction of the mainshaft 11 and the wall portion W1 so as to support the main shaft 11rotatably around the axis of the main shaft 11. That is, the main shaft11 is supported to the wall portion W1 via the double-row tapered rollerbearing 16.

Also, a coupling 17 (FIG. 3) is provided between the double-row taperedroller bearing 16 and the input shaft 12 a of the gear-box 12. That is,the main shaft 11 is connected to the input shaft 12 a via thedouble-row tapered roller bearing 16 and the coupling 17. In the presentembodiment, the coupling 17 is a gear coupling.

Next, a structure of the main shaft 11, supporting structure of the mainshaft 11 and connecting structure of the main shaft 11 and the gear-box12 will be described in detail with reference to FIGS. 1 to 3.

As shown in FIG. 2, the main shaft 11 is formed having a minor axis.Concretely, the main shaft 11 is formed in an approximately annularshape having its outer diameter D1 made larger than its axialdirectional length L1 (this may also be of an approximately disk shape).The main shaft 11 has its one end in the axial direction to which therotor head 4 is fitted provided with a first flange 11 a. To this firstflange 11 a, the rotor head 4 is fitted by bolting or the like.

Also, the main shaft 11 has the other end in the axial directionprovided with a second flange 11 b. To this second flange 11 b, thedouble-row tapered roller bearing 16 is connected by bolting or thelike.

As shown in FIGS. 2 and 3, the double-row tapered roller bearing 16comprises an outer ring 16 a connected to the wall portion W1 by boltingor the like, and an inner ring 16 b provided coaxially on the radialdirectional inner side of the outer ring 16 a. The main shaft 11 isconnected to the inner ring 16 b by bolting or the like.

In FIG. 3, between the outer ring 16 a and the inner ring 16 b, aplurality of rolling elements are provided along the circumferentialdirection. As the rolling elements, tapered rollers (conical rollers) Rare used.

Hereinbelow, with respect to the double-row tapered roller bearing 16,the tapered rollers R arranged along the circumferential direction atthe same position in the axial direction will be referred to as a row ofthe tapered rollers R. This row of the tapered rollers R is provided inplural rows along the axial direction (in the present embodiment, therow of the tapered rollers R is provided in two rows).

As further details of the construction of the double-row tapered rollerbearing 16, in an inner circumferential surface of the outer ring 16 a,an outer ring inclined surface C1, having its surface plane inclinedrelative to the axis, is provided along the entire circumferentialdirection. This outer ring inclined surface C1 is provided at two placesalong the axial direction and each of the outer ring inclined surfacesC1 has its inclination direction relative to the axis reversed to eachother.

In the present embodiment, the outer ring inclined surface C1 on themain shaft 11 side has its one end on the main shaft 11 side positionedon the radial directional outer side and the other end on the gear-box12 side positioned on the radial directional inner side. Also, the outerring inclined surface C1 on the gear-box 12 side has its one end on themain shaft 11 side positioned on the radial directional inner side andthe other end on the gear-box 12 side positioned on the radialdirectional outer side. That is, the inner circumferential surface ofthe outer ring 16 a, when seen on a cross section taken on the axis, isof a mountain shape.

Also, an inner ring inclined surface C2 is provided in an outercircumferential surface of the inner ring 16 b, at a position opposed toeach of the outer ring inclined surfaces C1. The inclination directionof each of the inner ring inclined surfaces C2 is the same as theinclination direction of the opposed outer ring inclined surface C1 andthe inclination angle of each of the inner ring inclined surfaces C2relative to the axis is set slightly smaller than the inclination angleof the opposed outer ring inclined surface C1.

In the present embodiment, the inner ring inclined surface C2 on themain shaft 11 side has its one end on the main shaft 11 side positionedon the radial directional outer side and the other end on the gear-box12 side positioned on the radial directional inner side. Also, the innerring inclined surface C2 on the gear-box 12 side has its one end on themain shaft 11 side positioned on the radial directional inner side andthe other end on the gear-box 12 side positioned on the radialdirectional outer side. That is, the outer circumferential surface ofthe inner ring 16 b, when seen on a cross section taken on the axis, isof a valley shape.

The tapered rollers R are provided along the circumferential directionbetween the outer ring inclined surface C1 and the inner ring inclinedsurface C2 of each pair and the row of the tapered rollers R is arrangedin two rows, one provided on the main shaft 11 side and one on thegear-box 12 side.

The tapered rollers R of each row are provided having their axesinclined in the same direction as the mutually opposed outer ringinclined surface C1 and inner ring inclined surface C2 relative to theaxis of the double-row tapered roller bearing 16.

More concretely, the tapered rollers R of each row have their smallerdiameter side positioned on the radial directional inner side and theirlarger diameter side positioned on the radial directional outer side.Thus, in the row of the tapered rollers R on the main shaft 11 side, thetapered rollers R are provided having their larger diameter sidedirected to the main shaft 11 side and their smaller diameter sidedirected to the gear-box 12 side. Also, in the row of the taperedrollers R on the gear-box 12 side, the tapered rollers R have theirlarger diameter side directed to the gear-box 12 side and their smallerdiameter side directed to the main shaft 11 side.

The coupling 17, as shown in FIGS. 2 and 3, is constructed by the innerring 16 b of the double-row tapered roller bearing 16, an inner tube 18and the input shaft 12 a. The inner tube 18 is of an approximatelycylindrical shape and is interposed substantially coaxially with theinput shaft 12 a between the double-row tapered roller bearing 16 andthe input shaft 12 a. The distal end portion of the input shaft 12 a isformed in a cylindrical shape so that one end of the inner tube 18 inthe axial direction can be inserted thereinto. If the gear-box 12 ismoved toward the generator 13 side, the inner tube 18 is drawn out ofthe input shaft 12 a so that the engagement of the input shaft 12 a withthe inner tube 18 is released.

As shown in FIG. 3, a first internal gear 21 is provided on an innercircumferential surface of the inner ring 16 b. Also, a first externalgear 22 is provided in an area of the inner tube 18 opposed to the innercircumferential surface of the inner ring 16 b, such that the firstexternal gear 22 meshes with the first internal gear 21.

In an area of the inner tube 18 inserted into the input shaft 12 a, asecond external gear 23 is provided and, on an inner surface of thedistal end portion of the input shaft 11, a second internal gear 24,that meshes with the second external gear 23, is provided.

The second internal gear 24 is made having a diameter smaller than thefirst internal gear 21 and thereby a torque transmission is carried outbetween the inner ring 16 b and the input shaft 12 a.

Next, a function of the power generating wind turbine 1 constructed asmentioned above will be described.

In the power generating wind turbine 1, the wind force working on thewind turbine rotating blades 5 from the rotational axis direction of therotor head 4 is converted into power to rotate the rotor head 4 aroundthe rotational axis thereof.

The rotation of the rotor head 4 is transmitted to the main shaft 11 tobe further transmitted from the main shaft 11 to the input shaft 12 avia the inner ring 16 b of the double-row tapered roller bearing 16 andthe inner tube 18 of the coupling 17. Then, this rotation is speeded upby the gear-box 12 to be inputted into the generator 13 via the outputshaft 12 b so that electric power is generated by the generator 13.

Here, at least while the electric power is being generated, in order toeffectively make use of the wind force working on the wind turbinerotating blades 5, the nacelle 3 is appropriately rotated on ahorizontal plane to be directed to the windward.

When the wind so hits on the wind turbine rotating blades 5, the mainshaft 11 receives not only a rotational torque but also a radial load,thrust load and bending load.

Nevertheless, in the power generating wind turbine 1 of the presentembodiment, such loads adding to the main shaft 11 are received by thedouble-row tapered roller bearing 16 that supports the main shaft 11 andlittle load except the rotational torque is transmitted to the inputshaft 12 a of the gear-box.

Next, a function of the double-row tapered roller bearing 16 will beconcretely described.

In the double-row tapered roller bearing 6, on the radial directionalouter side of the inner ring 16 b, the rows of the tapered rollers R areprovided. The outer ring 16 a is provided on the further radialdirectional outer side of the tapered rollers R, and this outer ring 16a is supported to the wall portion W1 of the nacelle bed plate 6.

That is, as the radial directional support of the inner ring 16 b iscarried out by the wall portion W1, even if the radial load adds to themain shaft 11, displacement of the main shaft 11 in the radial directioncan be suppressed to the minimum. In this way, even if the radial loadadds to the main shaft 11, this radial load is received by thedouble-row tapered roller bearing 16 and little radial load istransmitted to the input shaft 12 a of the gear-box 12.

Also, in the double-row tapered roller bearing 16, the row of thetapered rollers R is provided in two rows. That is, as the inner ring 16b is supported at two places along the axial direction, even if thebending load adds to the main shaft 11, the inclination of the mainshaft 11 can be suppressed to the minimum. In this way, even if thebending load adds to the main shaft 11, this bending load is received bythe double-row tapered roller bearing 16 and little bending load istransmitted to the input shaft 12 a of the gear-box 12.

On the other hand, in the double-row tapered roller bearing 16, on theinner circumferential surface of the outer ring 16 a, the outer ringinclined surface C1, being inclined relative to the axis, is provided intwo places along the axial direction and, on the outer circumferentialsurface of the inner ring 16 b, the inner ring inclined surface C2 isprovided being opposed to each of the outer ring inclined surfaces C1.

One pair of these outer ring inclined surface C1 and inner ring inclinedsurface C2 has its inclination direction relative to the axis reversedto the inclination direction of the other pair.

Thus, if the thrust load adds to the main shaft 11, whichever directionin the axial direction is the direction to which the thrust load adds,the inner ring inclined surface C2 is supported to the outer ringinclined surface C1 via the tapered rollers R in either one of the twopairs of the outer ring inclined surface C1 and the inner ring inclinedsurface C2.

That is, the inner ring 16 b is supported also in the axial direction bythe outer ring 16 a and the tapered rollers R and, even if the thrustload adds to the main shaft 11, this thrust load can be received by thedouble-row tapered roller bearing 16 and little thrust load istransmitted to the input shaft 12 a of the gear-box 12.

In this way, in the power generating wind turbine 1 of the presentembodiment, the main shaft 11 is supported by the single double-rowtapered roller bearing 16 and hence the supporting structure of the mainshaft 11 can be made compact.

Also, the radial load, thrust load and bending load so adding to themain shaft 11 can be received by the double-row tapered roller bearing16 and hence the strength required of the gear-box 12 and the gear-boxsupporting members can be made smaller.

By so reducing the required strength of the gear-box 12, the gear-box 12can be reduced in size and in weight as compared with the gear-box usedin the prior art power generating wind turbine.

Also, the main shaft 11 is formed in the annular shape in which theouter diameter D1 is larger than the axial directional length L1. Thatis, the length L (the axial directional size) of the main shaft 11 isset shorter than in the prior art main shaft.

Thereby, the weight of the main shaft 11 can be suppressed and thebending moment adding to the main shaft 11 when the wind turbinerotating blades 5 receive the wind force becomes smaller. Thus, thestrength required of the main shaft 11 and the supporting structure ofthe main shaft 11 can be made smaller.

By so making smaller the strength required of the main shaft 11 and thesupporting structure of the main shaft 11, the main shaft 11 and thesupporting structure of the main shaft 11 can be made further compact.

In this way, in the power generating wind turbine 1 of the presentembodiment, the parts and components provided in or on the nacelle 3,such as the supporting structure of the main shaft 11, the gear-box 12,the gear-box supporting members, etc. can be made smaller in size andlighter in weight and hence the nacelle 3 itself can be made smaller andlighter. Also, by so reducing the size and weight of the parts andcomponents provided in or on the nacelle 3, transportation andinstallation of the nacelle 3 and other parts and components can befacilitated. Further, the load adding to the tower 2 that supports theseparts and components becomes smaller and the structure of the tower 2can be simplified.

Moreover, in the power generating wind turbine 1 of the presentembodiment, the main shaft 11 and the gear-box 12 are structurallyseparate from each other. Hence, the maintenance of the main shaft 11and the gear-box 12 can be carried out independent from each other andthis realizes a high maintainability.

For example, in case of carrying out the maintenance of the gear-box 12,while the main shaft 11 is being fitted to the nacelle 3, the gear-box12 is separated from the main shaft 11 and the maintenance of thegear-box 12 only can be carried out. Also, in case of carrying out themaintenance of the main shaft 11, the main shaft 11 is separated fromthe gear-box 12 and the maintenance of the main shaft 11 only can becarried out.

Also, the main shaft 11 and the input shaft 12 a of the gear-box 12 areconnected together via the coupling 17 and hence the adjusting workrequiring skills, such as an alignment adjustment of the main shaft 11and the input shaft 12 a or the like becomes unnecessary and the work ofassembling and maintenance is facilitated.

By the coupling 17 also, transmission of the radial load, thrust loadand bending load from the main shaft 11 to the gear-box 12 can beprevented and thereby the strength required of the gear-box 12 and thegear-box supporting members can be made further smaller.

Moreover, in the present embodiment, the main shaft 11 and the gear-box12 are connected together via the coupling 17 being a gear coupling. Bydrawing the gear-box 12 out of the main shaft 11 so that the coupling 17is released, the main shaft 11 and the gear-box 12 can be easilyseparated from each other. In this way, in the power generating windturbine 1 of the present embodiment, the main shaft 11 and the gear-box12 can be easily separated from each other and this realizes a highmaintainability.

Here, in the present embodiment, while the example where the coupling 17is a gear coupling has been shown, the invention is not limited theretobut a disk coupling, connecting structure by a bush, connectingstructure by a pin or otherwise a coupling of an arbitrary type can beused.

Second Embodiment

A second embodiment according to the present invention will be describedbelow with reference to FIG. 4. A power generating wind turbine 31 ofthe present embodiment, as shown in FIG. 4, is partially different fromthe power generating wind turbine 1 of the first embodiment. In thepower generating wind turbine 31 to be described below, parts andcomponents same or similar to those of the power generating wind turbine1 are designated by the same reference numerals and detailed descriptionon the already described ones will be omitted.

The power generating wind turbine 31 of the present embodiment is mainlycharacterized in being different from the power generating wind turbine1 in the shape of the main shaft, supporting structure of the main shaftand construction of the gear-box.

In the power generating wind turbine 31 shown in FIG. 4, as the mainshaft to which the rotor head 4 is connected, a main shaft 32 having aminor axis is employed. Concretely, the main shaft 32 is of anapproximately annular shape in which an outer diameter D2 is larger thanan axial directional length L2 (this may also be of an approximatelydisk shape).

It is to be noted that the rotor head 4 and the main shaft 32 areconnected together by an arbitrary connecting structure, such as boltingor the like.

The main shaft 32 has its outer circumference received by the inner ring16 b of the double-row tapered roller bearing 16 so that the main shaft32 is supported to the nacelle bed plate 6 via the double-row taperedroller bearing 16.

Also, the main shaft 32 has its radial directional inner side connectedto an input shaft 34 a of a gear-box 34 via a coupling 33. The inputshaft 34 a is connected coaxially with the main shaft 32 so that arotation of the input shaft 34 a around the axis relative to the mainshaft 32 is regulated.

As the coupling 33, a gear coupling, for example, is used that comprisesan internal gear provided on an inner circumferential surface of themain shaft 32 and an external gear provided on an outer circumferentialsurface of the input shaft 34 a so as to mesh with the internal gear.Here, the coupling 33 is not limited to the gear coupling but a diskcoupling, connecting structure by a bush, connecting structure by a pinor otherwise a coupling of an arbitrary type can be used.

The gear-box 34 speeds up the rotation inputted into the input shaft 34a from the main shaft 32 to an appropriate rotational speed to be putout to an output shaft 34 b. The gear-box 34 has its portion, other thanan input shaft end and an output shaft end, contained in a casing 34 c.

Between the input shaft 34 a and the output shaft 34 b, a planetarystage 36 using planetary gears and a parallel stage 37 using spur gears,connected in series to the planetary stage 36, are provided and thespeed-up is carried out in each of these stages. In the presentembodiment, the gear-box 34 has the planetary stage 36 of one stage andthe parallel stage 37 of two stages so that the rotation inputted fromthe input shaft 34 a can be speeded up to an appropriate rotationalspeed by the speed-up of three stages.

The planetary stage 36 is of what is called a planetary type providedbetween the input shaft 34 a and the parallel stage 37. Concretely, theplanetary stage 36 comprises a sun gear 41 provided on an input shaft 37a of the parallel stage 37, an internal gear 42 of an annular shapeprovided coaxially with the sun gear 41 at the same position in theaxial direction and planetary gears 43, 44 of a pair provided betweenthe sun gear 41 and the internal gear 42 for meshing therewith.

The internal gear 42 is fixedly fitted to the casing 34 c by a stay orthe like (not shown) so that a rotation of the internal gear 42 aroundthe axis relative to the casing 34 c is regulated.

The planetary gears 43, 44 of the pair are provided at positions opposedto each other with the sun gear 42 being interposed between them andsupporting shafts 43 a, 44 a of the planetary gears 43, 44,respectively, are supported to the input shaft 34 a of the gear-box 34.

The input shaft 34 a of the gear-box 34 is provided coaxially with themain shaft 32 and comprises a disk portion 46 (this may also be anannular portion) to be inserted into the radial directional inner sideof the main shaft 32 and a bearing portion 47 provided projecting towardthe planetary gears 43, 44 side from the disk portion 46 and supportingthe supporting shafts 43 a, 44 a of the planetary gears 43, 44 so thattheir rotation around the axis is allowed.

In the power generating wind turbine 31 constructed as mentioned above,when the main shaft 32 is rotationally driven around the axis by thewind force, the input shaft 34 a of the gear-box 34 connected to themain shaft 32 via the coupling 33 also is rotated around the axistogether with the main shaft 32.

Then, the planetary gears 43, 44 supported by the bearing portion 47 ofthe input shaft 34 a are rotated (revolved) around the axis of the inputshaft 34 a.

Also, by the input shaft 34 a being rotationally driven around the axis,the planetary gears 43, 44 meshing with the fixedly fitted internal gear42 are rotated around the supporting shafts 43 a, 44 a, respectively.

By the respective planetary gears 43, 44 being so rotated, the sun gear41 meshing with the planetary gears 43, 44 is rotationally driven aroundthe axis together with the input shaft 37 a of the parallel stage 37.

In this way, the planetary stage 36 speeds up the rotation of the mainshaft 32 by one stage to be transmitted to the parallel stage 37. Theparallel stage 37 speeds up the rotation inputted into the input shaft37 a further by two stages to be put out to the output shaft 34 b. Then,the rotation of the output shaft 34 b is inputted into the generator 13so that electricity is generated by the generator 13.

In the power generating wind turbine 31 having the above-mentionedconstruction, a gear-box having a construction different from thegear-box 34 may be employed.

Herebelow, construction examples of the gear-box employed other thanthat of the power generating wind turbine of the present embodiment willbe described with reference to FIGS. 5 to 7.

A gear-box 51 shown in FIG. 5 (First Example) employs a planetary stage52 of what is called a star type in place of the planetary stage 36 ofthe gear-box 34 shown in FIG. 4. Concretely, while, in the planetarystage 36, the supporting shafts 43 a, 44 a of the planetary gears 43, 44are supported to the input shaft 34 a, in the construction of theplanetary stage 52, they are supported by a stay 53 connected to thecasing 34 c (not shown in FIG. 5).

Here, the supporting shafts 43 a, 44 a are supported so that theirrotation (revolution) around the sun gear 41 is regulated and theplanetary gears 43, 44 are supported rotatably around their axes.

Also, in the planetary stage 52, in place of providing the input shaft34 a and the internal gear 42, an input shaft 51 a is provided. Theinput shaft 51 a comprises a columnar portion 56 (this may also be acylindrical portion) to be coaxially inserted into the radialdirectional inner side of the main shaft 32 and an internal gear 57provided on the sun gear 41 side of the columnar portion 56 for meshingwith the planetary gears 43, 44.

Here, the columnar portion 56 also is connected to the main shaft 32 viathe coupling 33.

In the gear-box 51 constructed as mentioned above, when the main shaft32 is rotationally driven around the axis by the wind force, the inputshaft 51 a of the gear-box 51 connected to the main shaft 32 via thecoupling 33 also is rotated around the axis together with the main shaft32.

Then, the respective planetary gears 43, 44 meshing with the internalgear 57 of the input shaft 51 a are rotated around their axes.

By the respective planetary gears 43, 44 being so rotated, the sun gear41 meshing with the planetary gears 43, 44 is rotationally driven aroundthe axis together with the input shaft 37 a of the parallel stage 37.

In this way, in the planetary stage 52, the rotation of the main shaft32 is speeded up by one stage to be transmitted to the parallel stage37.

A gear-box 61 shown in FIG. 6 (Second Example) employs a planetary stage62 of what is called a compound planetary type in place of the planetarystage 36 of the gear-box 34 shown in FIG. 4. Concretely, in theplanetary stage 62, the sun gear 41, that has meshed with the internalgear 42 in the planetary stage 36, is arranged being moved toward theparallel stage 37 side beyond the internal gear 42. And, in place of theplanetary gears 43, 44, there are provided first planetary gears 63, 64meshing with the sun gear 41 and second planetary gears 66, 67 arrangedon the input shaft 34 a side of these first planetary gears 63, 64 so asto mesh with the internal gear 42.

The first planetary gear 63 and the second planetary gear 66 arecoaxially supported by a supporting shaft 68, that is supported to theinput shaft 34 a, so that their relative rotations around the axis areregulated. Likewise, the first planetary gear 64 and the secondplanetary gear 67 are coaxially supported by a supporting shaft 69, thatis supported to the input shaft 34 a, so that their relative rotationaround the axis is regulated.

Here, the first planetary gear 63 and the second planetary gear 66 arerotatable around the axis together with the supporting shaft 68.Likewise, the first planetary gear 64 and the second planetary gear 67are rotatable around the axis together with the supporting shaft 69.

In the gear-box 61, when the input shaft 34 a rotates, the secondplanetary gears 66, 67 supported to the input shaft 34 a rotate(revolve). When the second planetary gears 66, 67, meshing with theinternal gear 42, so rotate, they rotate together with the supportingshafts 68, 69.

In this way, when the second planetary gears 66, 67 rotate, the firstplanetary gears 63, 64 connected to these second planetary gears 66, 67via the supporting shafts 68, 69 also rotate. Thereby, the sun gear 41meshing with these first planetary gears 63, 64 is rotationally drivenand the rotation is inputted into the downstream parallel stage 37.

In the gear-box 61, the sun gear 41 and the first planetary gears 63, 64are positioned on the parallel stage 37 side beyond the internal gear 42and hence the size of the set of these gears is not needed to be madeinstallable within the size of the inner diameter of the internal gear42.

That is, in the gear-box 61, the diameter of the first planetary gears63, 64 can be made larger than the second planetary gears 66, 67 and,between these first and second planetary gears, the speed-up of onestage can be carried out.

Thereby, in the gear-box 61, the speed-up ratio can be further enhancedas compared with the gear-box 34 shown in FIG. 4.

A gear-box 71 shown in FIG. 7 (Third Example) employs a planetary stage72 of what is called a compound planetary type in place of the planetarystage 52 of the gear-box 51 shown in FIG. 5. Concretely, in theplanetary stage 72, the sun gear 41, that has meshed with the internalgear 42 in the planetary stage 52, is arranged being moved toward theparallel stage 37 side beyond the internal gear 42. And, in place of theplanetary gears 43, 44, there are provided first planetary gears 73, 74meshing with the sun gear 41 and second planetary gears 76, 77 arrangedon the input shaft 34 a side of these first planetary gears 73, 74 so asto mesh with the internal gear 42.

The first planetary gear 73 and the second planetary gear 76 areprovided on a supporting shaft 78, that is supported to a casing (notshown) via a stay 80 and these first planetary gear 73 and secondplanetary gear 76 are coaxially supported by the supporting shaft 78 sothat their relative rotation around the axis is regulated. Likewise, thefirst planetary gear 74 and the second planetary gear 77 are provided ona supporting shaft 79, that is supported to the casing via the stay 80and these first planetary gear 74 and the second planetary gear 77 arecoaxially supported by the supporting shaft 79 so that their relativerotation around the axis is regulated.

Here, the first planetary gear 73 and the second planetary gear 76 arerotatable around the axis together with the supporting shaft 78.Likewise, the first planetary gear 74 and the second planetary gear 77are rotatable around the axis together with the supporting shaft 79.

In the gear-box 71, when the input shaft 51 a rotates, the secondplanetary gears 76, 77 meshing with the internal gear 57 of the inputshaft 51 a rotate.

By the second planetary gears 76, 77 so rotating, the first planetarygears 73, 74 connected to these second planetary gears 76, 77 via thesupporting shafts 78, 79 also rotate. Thereby, the sun gear 41 meshingwith these first planetary gears 73, 74 is rotationally driven and therotation is inputted into the downstream parallel stage 37.

In this gear-box 71 also, the sun gear 41 and the first planetary gears73, 74 are positioned on the parallel stage 37 side beyond the internalgear 42 and hence the size of the set of these gears is not needed to bemade installable within the size of the inner diameter of the internalgear 42.

Thus, the diameter of the first planetary gears 73, 74 can be madelarger than the second planetary gears 76, 77 and, between these firstand second planetary gears, the speed-up of one stage can be carriedout.

Thereby, in the gear-box 71, the speed-up ratio can be further enhancedas compared with the gear-box 51 shown in FIG. 5.

It is to be noted that the constructions of the above-describedgear-boxes 51, 61, 71 are also applicable to the gear-box 12 of thepower generating wind turbine 1 of the first embodiment.

Here, as the generator 13 shown in each of the above embodiments, amultipolar generator may be used.

The multipolar generator can generate a sufficient electric power, evenif the rotational speed of the generator shaft of the generator 13 islow. That is, as the speed-up ratio of the gear-box can be made smaller,such a gear-box as effects a speed-up of one stage only can be used asthe gear-box.

For example, as shown in FIG. 8, as the gear-box, a gear-box 81comprising the above-mentioned planetary stage 36 only can be used. Or,as shown in FIG. 9, a gear-box 82 comprising the above-mentionedplanetary stage 52 only can be used.

It is to be noted that, in the generator, the greater the number ofpoles, the further the lower limit of the rotational speed of thegenerator shaft at which electricity can be stably generated can bereduced. Hence, it is preferable to use a generator having poles ofeight or more.

Also, in the schematic views of FIGS. 8 and 9, while examples where agear-box carrier and a generator stator are directly assembled onto thenacelle bed plate 6 are shown, a casing of the gear-box 81 or 82 or acasing of the generator 13 may be assembled onto the nacelle bed plate6.

Such a gear-box performing a speed-up of one stage only can be madeextraordinarily small in size and light in weight as compared with theprior art gear-box performing the speed-up of multiple stages. Also,such a gear-box uses less number of gears and hence the reliabilitybecomes high and troublesome maintenances can be largely saved. Also,noise of the gear-box is small and this gives less influence on thesurrounding environment.

Here, in a synchronous type generator, there is a need to adjust theoutput to an appropriate level by inputting all the generated power intoa power converting apparatus and hence a comparatively large type powerconverting apparatus is needed to be installed on the nacelle 3.Contrary to this, in an induction type generator (for example, adouble-fed type or a rotor current control type), the conversion iscarried out by inputting only the secondary side output into an inverterand the nacelle 3 may be provided with a small type inverter. For thisreason, by using the induction type generator, the space on the nacelle3 can be efficiently used as compared with the case of using thesynchronous type generator.

Also, in each of the above-described embodiments, while examples wherethe main shaft and the rotor head are separate members from each otherare shown, the invention is not limited thereto but, for example, acombined member 86 in which the main shaft 11 and the rotor head 4 areintegrated together, as shown in FIG. 10, may be used. Such combinedmember 86 can be manufactured by casting, for example.

In this construction, assembling work to assemble together the rotorhead and the main shaft becomes unnecessary and man-hour to assemble thepower generating wind turbine can be reduced. Also, a fitting flange ofthe main shaft becomes unnecessary and a weight alleviation of theentire device can be realized as compared with the case where the mainshaft and the rotor head are separated from each other.

Also, in each of the above-described embodiments, while examples wherethe coupling is used as the connecting structure of the main shaft andthe input shaft of the gear-box are shown, the invention is not limitedthereto but, for example, a connecting structure shown in FIG. 11 may beused.

That is, in the connecting structure of FIG. 11, the second externalgear 23 arranged on the inner tube 18 and the second internal gear 24arranged on the input shaft 12, both provided in the first embodiment,are eliminated and instead a tapered ring member 87 is inserted alongthe axial direction by using a bolt or hydraulic pressure around anouter circumferential surface of an area where the second external gear23 has been arranged. This tapered ring member 87, when seen on a crosssection taken on the axis, is formed in a wedge shape in which an outerdiameter is gradually contracted toward the input shaft 12 a side.

In the present connecting structure, the tapered ring member 87 providedaround the outer circumferential surface of the inner tube 18 isforcibly inserted under the inner surface of the input shaft 12 a andthereby a large friction force is generated by a surface pressurebetween the tapered ring member 87 and the input shaft 12 a. Thus, bythis friction force, the rotation transmitted from the main shaft 11 tothe inner tube 18 is further transmitted to the input shaft 12 a via thetapered ring member 87.

Third Embodiment

Next, a third embodiment according to the present invention will bedescribed with reference to FIG. 12.

A power generating wind turbine 91 of the present embodiment, as shownin FIG. 12, is partially different from the power generating windturbine 1 of the first embodiment. In the power generating wind turbine91 to be described below, parts and components same or similar to thoseof the power generating wind turbine 1 are designated by the samereference numerals and detailed description on the already describedones will be omitted.

The power generating wind turbine 91 of the present embodiment is mainlycharacterized in being different from the power generating wind turbine1 in the supporting structure of the main shaft. Concretely, in thepower generating wind turbine 91, as the supporting structure supportingthe main shaft 11, in place of the double-row tapered roller bearing 16,such a structure is employed that the main shaft 11 is supported to thenacelle 3 via a single three-row roller bearing 92 that comprises a rowof rollers receiving the radial load and a pair of rows of rollersreceiving the thrust load.

The three-row roller bearing 92 is provided coaxially with the mainshaft 11 between an axial directional one end of the main shaft 11 andthe wall portion W1 so as to support the main shaft 11 rotatably aroundits axis. That is, the main shaft 11 is supported to the wall portion W1via the three-row roller bearing 92.

The three-row roller bearing 92 comprises an outer ring 92 a, that isconnected to the wall portion W1 by bolting or the like, and an innerring 92 b, that is coaxially provided on the radial directional innerside of the outer ring to be connected to the main shaft 11 by boltingor the like.

Between these outer ring 92 a and inner ring 92 b, a plurality ofrolling elements are provided along the circumferential direction. Asthe rolling elements, cylindrical rollers Rc are used. Herebelow, in thethree-row roller bearing 92, the cylindrical rollers Rc arranged alongthe circumferential direction at the same position in the axialdirection will be referred to as a row of the rollers Rc. This row ofthe rollers Rc is provided in three rows along the axial direction.

As further details of the construction of the three-row roller bearing92, in an inner circumferential surface of the outer ring 92 a, a firstgroove 93 is provided along the entire circumferential direction. Thisfirst groove 93, when seen on a cross section taken on the axis, has arectangular shape extending in the radial direction. Also, in a bottomsurface of the first groove 93, a second groove 94 is provided along theentire circumferential direction. This second groove, when seen on across section taken on the axis, has a rectangular shape extending inthe radial direction and having a width smaller than the first groove93.

The first groove 93 has its side wall 93 a formed in a plane that iscoaxial with the outer ring 92 a and substantially orthogonal to theaxis of the outer ring 92 a. Also, the second groove 94 has its bottomsurface 94 a formed in a cylindrical surface that is coaxial with theouter ring 92 a.

In an area opposed to the first groove 93 a of an outer circumferentialsurface of the inner ring 92 b, a projection 95 is provided along theentire circumferential direction. This projection 95, when seen on across section taken on the axis, has a rectangular shape extending inthe radial direction and is positioned within the first groove 93 aformed in the outer ring 92 a.

The projection 95 has its side wall 95 a formed in a plane that issubstantially orthogonal to the axis of the inner ring 92 b and itsouter circumferential surface 95 b formed in a cylindrical surface thatis coaxial with the inner ring 92 b.

That is, both of the side wall 93 a of the first groove 93 and the sidewall 95 a of the projection 95 have planes parallel with each other andboth of the bottom surface 94 a of the second groove 94 and the outercircumferential surface 95 b of the projection 95 have cylindricalsurfaces parallel to each other.

Between these side wall 93 a and side wall 95 a, a plurality ofcylindrical rollers Rc are provided. These cylindrical rollers Rc areprovided having their respective axes arranged along the radialdirection of the three-row roller bearing 92. The row so formed by thesecylindrical rollers Rc will be called a first row of rollers R1.

Also, between the bottom surface 94 a and the outer circumferentialsurface 95 b, a plurality of cylindrical rollers Rc are provided. Thesecylindrical rollers Rc are provided having their respective axesarranged substantially in parallel with the axis of the three-row rollerbearing 92. The row so formed by the cylindrical rollers Rc will becalled a second row of rollers R2.

In the power generating wind turbine 91 constructed as mentioned above,the load adding to the main shaft 11 is received by the wall portion W1via the three-row roller bearing 92 that supports the main shaft 11 andlittle load except the rotational torque is transmitted to the inputshaft 12 a of the gear-box 12.

Next, a function of the three-row roller bearing 92 will be concretelydescribed.

Both axial directional side surfaces of the projection 95 of the innerring 92 b to which the main shaft 11 is fitted are supported to theouter ring 92 a via the two first rows of rollers R1. For this reason,when the thrust load adds to the main shaft 11, this thrust load isreceived by the outer ring 92 a, while a rotation of the inner ring 92 brelative to the outer ring 92 a is being allowed.

Also, the first rows of rollers R1 are provided on both sides of theprojection 95 so that the projection 95 is supported from both sides inthe axial direction to the outer ring 92 a. Hence, even if the bendingload adds to the main shaft 11, this bending load is received by theouter ring 92 a, while a rotation of the inner ring 92 b relative to theouter ring 92 a is being allowed.

Also, between the outer circumferential surface 95 b of the projection95 on the inner ring 92 b and the bottom surface 94 a of the secondgroove 94 provided in the outer ring 92 a, the second row of rollers R2is provided. Thus, the outer circumferential surface of the inner ring92 b is supported to the outer ring 92 a via the second row of rollersR2. Hence, when the radial load adds to the main shaft 11, this radialload is received by the outer ring 92 a, while a rotation of the innerring 92 b relative to the outer ring 92 a is being allowed.

As the outer ring 92 a is fitted to the wall portion W1 of the nacelle3, the thrust load, bending load and radial load transmitted from themain shaft 11 to the inner ring 92 b are received by the wall portion W1via the three-row roller bearing 92.

In this way, in the power generating wind turbine 91 of the presentembodiment, the main shaft 11 is supported by the single three-rowroller bearing 92 and hence the supporting structure of the main shaft11 can be made compact.

Also, the radial load, thrust load and bending load adding to the mainshaft 11 are received by the three-row roller bearing 92 and hence thestrength required of the gear-box 12 and the supporting members thereofcan be made lower.

By so reducing the required strength of the gear-box 12, a gear-boxwhich is smaller in size and lighter in weight can be used for thegear-box 12, as compared with that used in the prior art powergenerating wind turbine.

It is to be noted that, while the present embodiment has been describedwith respect to the example where the power generating wind turbine 91is applied to the first embodiment, the power generating wind turbine 91may be applied to the construction of the power generating wind turbineof the second embodiment or the constructions of the modificationexamples of the first and second embodiments.

1. A power generating wind turbine comprising: a nacelle supported by atower; a main shaft connected to a wind turbine rotating blade at afront side of a wall portion of said nacelle; a generator housed withinsaid nacelle; and a gear-box for increasing a rotational speed of anoutput shaft of said gearbox to drive said generator, said gear-boxbeing housed within said nacelle, wherein said main shaft is connectedto an input shaft of said gear-box, and said main shaft is supported bysaid wall portion of said nacelle via a single double-row tapered rollerbearing provided coaxially with said main shaft, said single double-rowtapered roller bearing being positioned at the front side of said wallportion and at an axial end portion of said main shaft.
 2. A powergenerating wind turbine according to claim 1, wherein said main shafthas an annular or disk shape and an outer diameter of said main shaft islarger than an axial directional length of said main shaft.
 3. A powergenerating wind turbine according to claim 2, wherein said main shaftand said input shaft of said gear-box are connected to each other via acoupling.
 4. A power generating wind turbine according to claim 1,wherein said main shaft and said input shaft of said gear-box areconnected to each other via a coupling.
 5. A power generating windturbine comprising: a nacelle supported by a tower; a main shaftconnected to a wind turbine rotating blade at a front side of a wallportion of said nacelle; a generator housed within said nacelle; and agear-box for increasing a rotational speed of an output shaft of saidgearbox to drive said generator, said gear-box being housed within saidnacelle, wherein said main shaft is connected to an input shaft of saidgear-box, and said main shaft is supported by said wall portion of saidnacelle via a single three-row roller bearing provided coaxially withsaid main shaft, said single three-row roller bearing having a first rowof rollers for receiving a radial load and second and third rows ofrollers for receiving a thrust load, said single three-row rollerbearing being positioned at the front side of said wall portion and atan axial end portion of said main shaft.
 6. A power generating windturbine according to claim 5, wherein said main shaft has an annular ordisk shape and an outer diameter of said main shaft is larger than anaxial directional length of said main shaft.
 7. A power generating windturbine according to claim 6, wherein said main shaft and said inputshaft of said gear-box are connected to each other via a coupling.
 8. Apower generating wind turbine according to claim 5, wherein said mainshaft and said input shaft of said gear-box are connected to each othervia a coupling.